To evaluate the effectiveness of dialysis and manage patient treatment, it is important to determine with some precision the mass transfer of blood in the dialysate, as well as water and various dissolved substances such as urea, and salts such as sodium, potassium and phosphates. These values are presently calculated from measurements known as "clearances" derived from the blood flow rate through the artificial kidney and from plasma concentrations at the input and output of the kidney. This involves hypotheses about the kinetics of transfers which are invalid for numerous dissolved substances. A far more reliable method, known in the art but not currently used, consists of collecting all the dialysate, that is 80 to 150 liters per session per patient, and after thoroughly homogenizing it, measuring the total volume of dialysate and measuring the concentration of dissolved elements. For this reason, the methods currently used consist of sampling the dialysate and drawing off the amount of material required for analysis. Relatively complex equipment is used for this procedure. Such an apparatus is described, for example, in U.S. Pat. No. 3,512,418, which, is theoretically designed to draw off a predetermined percentage of a liquid substance circulating through a conduit. Similar devices are described in U.S. Pat. No. 3,942,388 and French Patent No. 1.181.412.
Unfortunately, the apparatus or the devices lack precision and fail to obtain a sample of material for analysis which is an exact reflection of the total material evacuated. This is a ms, or flaw, especially in the case of analyzing dialysate evacuated by a dialysis machine. For this particular application it is essential that the sample correspond exactly to the dialysate exiting the machine so the parameters of the dialysis procedure can be precisely adjusted.
The present invention proposes a device for implementing this procedure which collects a dialysate sample that accurately represents the composition of the total dialysate and the volume of which is a known proportion of the total dialysate volume.